1. Field of the Invention
The present invention relates to a method of manufacturing a solid-state image sensor.
2. Description of the Related Art
There is known a technique of improving the light condensing performance by forming a light waveguide made of a high refractive index material in a region on a photoelectric converter such as a photodiode which forms a pixel so that light is totally reflected by the interface of the light waveguide (see Japanese Patent Laid-Open Nos. 05-235313 and 2004-193500). A typical example of the material of this light waveguide is silicon nitride deposited using the high density plasma CVD (Chemical Vapor Deposition) method.
The use of silicon nitride as the material of a light waveguide poses a problem associated with heat stress resulting from the difference in thermal expansion coefficient between the nitride silicon and an insulating film which surrounds it. When an opening is formed in an insulating film on a photoelectric converter and filled with silicon nitride so as to form a light waveguide, a process defect may be generated by heat stress acting between the silicon nitride and the insulating film. Examples of this process defect include an increase in manufacturing variation due to warping of a silicon wafer, the occurrence of a crack in the insulating film, or an increase in leakage current of a chip.